Synchronization and broadcast channel design with flexible bandwidth allocations

ABSTRACT

Certain aspects of the present disclosure provide various synchronization channel and physical broadcast channel (PBCH) designs. A method for wireless communications by a user equipment (UE). The UE detects a synchronization channel and a secondary synchronization signal (SSS) transmitted with the synchronization channel. The UE demodulates a PBCH based on the SSS and determines system bandwidth corresponding to the downlink bandwidth based on system information in the PBCH.

CROSS-REFERENCE TO RELATED APPLICATION & PRIORITY CLAIM

This application is a Continuation of U.S. application Ser. No.15/726,345, filed Oct. 5, 2017, and claims benefit of and priority toU.S. Provisional Patent Application Ser. No. 62/405,860, filed Oct. 7,2016, both herein incorporated by reference in their entirety for allapplicable purposes.

TECHNICAL FIELD

Aspects of the present disclosure relate generally to wirelesscommunications systems, and more particularly, to synchronization andbroadcast channel design for certain systems, such as new radio (NR)systems, that may use flexible bandwidth allocations and/orsynchronization channels not centered around a direct tone (DC) tone.

INTRODUCTION

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, data,messaging, broadcasts, etc. The systems may employ multiple-accesstechnologies capable of supporting communication with multiple users bysharing available system resources (e.g., bandwidth and transmit power).Examples of such multiple-access systems include 3rd GenerationPartnership Project (3GPP) Long Term Evolution (LTE) systems, LTEAdvanced (LTE-A) systems, code division multiple access (CDMA) systems,time division multiple access (TDMA) systems, frequency divisionmultiple access (FDMA) systems, orthogonal frequency division multipleaccess (OFDMA) systems, single-carrier frequency division multipleaccess (SC-FDMA) systems, and time division synchronous code divisionmultiple access (TD-SCDMA) systems.

In some examples, a wireless multiple-access communication system mayinclude a number of base stations (BSs) that each can simultaneouslysupport communication for multiple communication devices, otherwiseknown as user equipment (UEs). In LTE or LTE-A network, a set of one ormore base stations may define an e NodeB (eNB). In other examples (e.g.,in a NR, next generation or 5G network), a wireless multiple accesscommunication system may include a number of distributed units (DUs)(e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smartradio heads (SRHs), transmission reception points (TRPs), etc.) incommunication with a number of central units (CUs) (e.g., central nodes(CNs), access node controllers (ANCs), etc.), where a set of one or moredistributed units, in communication with a central unit, may define anaccess node (e.g., a new radio base station (NR BS), a new radio node-B(NR NB), a network node, 5G NB, a Next Generation Node B (gNB), etc.).BS or DU may communicate with a set of UEs on downlink channels (e.g.,for transmissions from a BS or to a UE) and uplink channels (e.g., fortransmissions from a UE to a BS or DU).

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is new radio (NR), for example, 5G radioaccess. NR is a set of enhancements to the LTE mobile standardpromulgated by Third Generation Partnership Project (3GPP). It isdesigned to better support mobile broadband Internet access by improvingspectral efficiency, lowering costs, improving services, making use ofnew spectrum, and better integrating with other open standards usingOFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink(UL) as well as support beamforming, multiple-input multiple-output(MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in NR technology.Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

BRIEF SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects of the present disclosure generally relate to techniquesfor synchronization and broadcast channel design and signaling.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a user equipment (UE). The method generally includesdetecting a synchronization channel and a secondary synchronizationsignal (SSS) transmitted with the synchronization channel. The UEdemodulates a physical broadcast channel (PBCH) based on the SSS. The UEdetermines system bandwidth corresponding to the downlink bandwidthbased on system information in the PBCH.

Certain aspects of the present disclosure provide an apparatus forwireless communications, such as a UE. The apparatus generally includesmeans for detecting a synchronization channel and a SSS transmitted withthe synchronization channel. The apparatus demodulates a PBCH based onthe SSS. The apparatus determines system bandwidth corresponding to thedownlink bandwidth based on system information in the PBCH.

Certain aspects of the present disclosure provide an apparatus forwireless communications, such as a UE. The apparatus generally includesat least one processor coupled with a memory and configured to detect asynchronization channel and a SSS transmitted with the synchronizationchannel. The at least one processor demodulates a PBCH based on the SSS.The at least one processor determines system bandwidth corresponding tothe downlink bandwidth based on system information in the PBCH.

Certain aspects of the present disclosure provide a computer readablemedium having computer executable code stored thereon for wirelesscommunications, such as by a UE. The computer readable medium generallyincludes code for detecting a synchronization channel and a SSStransmitted with the synchronization channel. The computer readablemedium includes code for demodulating a PBCH based on the SSS anddetermining system bandwidth corresponding to the downlink bandwidthbased on system information in the PBCH.

Certain aspects of the present disclosure also provide a method forwireless communications by a base station that may be consideredcomplementary to the UE operations above (e.g., for generating thesynchronization and PBCH channels detected and read by the UE).

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram illustrating an example logical architectureof a distributed radio access network (RAN), in accordance with certainaspects of the present disclosure.

FIG. 3 is a diagram illustrating an example physical architecture of adistributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 4 is a block diagram conceptually illustrating a design of anexample base station (BS) and user equipment (UE), in accordance withcertain aspects of the present disclosure.

FIG. 5 is a diagram showing examples for implementing a communicationprotocol stack, in accordance with certain aspects of the presentdisclosure.

FIG. 6 illustrates an example of a downlink-centric subframe, inaccordance with certain aspects of the present disclosure.

FIG. 7 illustrates an example of an uplink-centric subframe, inaccordance with certain aspects of the present disclosure.

FIG. 8 illustrates an example of a wireless communication systemsupporting zones, in accordance with certain aspects of the presentdisclosure.

FIG. 9 illustrated an example synchronization channel centered around aDC tone.

FIG. 10 is a flow diagram illustrating example operations that may beperformed by a user equipment (UE) for demodulating a physical broadcastchannel (PBCH) based on the a secondary synchronization signal (SSS) toobtain system information, in accordance with certain aspects of thepresent disclosure.

FIG. 11 illustrates an example synchronization channel design, inaccordance with certain aspects of the present disclosure.

FIG. 12 illustrates an example reference signal (RS) design centeredaround a synchronization channel that is not centered around a DC tone,in accordance with certain aspects of the present disclosure.

FIG. 13 illustrates an example punctured RS and synchronization channeldesign, in accordance with certain aspects of the present disclosure.

FIG. 14 illustrates an example synchronization channel design includingan indication of the synchronization channel offset, in accordance withcertain aspects of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processingsystems, and computer readable mediums for operations that may beperformed in NR applications (new radio access technology or 5Gtechnology). NR may support various wireless communication services,such as Enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g.80 MHz beyond), millimeter wave (mmW) targeting high carrier frequency(e.g., 27 GHz or beyond), massive MTC (mMTC) targeting non-backwardcompatible MTC techniques, and/or mission critical targeting ultrareliable low latency communications (URLLC). These services may includelatency and reliability requirements. These services may also havedifferent transmission time intervals (TTI) to meet respective qualityof service (QoS) requirements. In addition, these services may co-existin the same subframe.

In certain systems, such as long term evolution (LTE), thesynchronization channel (e.g., carrying primary synchronization signal(PSS), secondary synchronization signal (SSS), and physical broadcastchannel (PBSCH)) are centered around the direct current (DC) tone(carrier) of the system bandwidth and may include system information fora user equipment (UE). The DC tone is a null tone that helps the UElocate the center of the system bandwidth. The cell-specific referencesignal (CRS) is also centered around the DC tone. Thus, even before theUE gets downlink bandwidth information from the PBCH, the UE candetermine the CRS sequence centered around the DC tone and the CRS canbe used to demodulate the PBCH. Once the PBCH is received, the UE canuse the downlink bandwidth information for a random access channel(RACH) procedure with the cell.

In some systems (e.g., NR, unlicensed/shared spectrum, narrowbandInternet-of-Things (NB-IoT)), however, the synchronization channeland/or CRS may not be centered around the DC tone. Thus, designs for thesignaling are desirable, which will allow the UE to receive/demodulatethe PBCH and to obtain the system information, even when the UE does notknow the downlink bandwidth and the locations may not be centered aroundthe DC tone.

Aspects of the present disclosure provide synchronization and broadcastdesigns that may be used for flexible bandwidth allocations. In oneexample, PBCH is demodulated with a secondary synchronization signal(SSS). In another example, PBCH is demodulated with a measurementreference signal (MRS). In another example, the offset of thesynchronization channel with respect to the DC tone is signaled to theUE. In yet another example, the UE performs multiple hypothesis PNCHdecoding.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in some other examples. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim. The word “exemplary”is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

The techniques described herein may be used for various wirelesscommunication networks such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as NR (e.g. 5GRA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA andE-UTRA are part of Universal Mobile Telecommunication System (UMTS). NRis an emerging wireless communications technology under development inconjunction with the 5G Technology Forum (5GTF). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that useE-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, while aspects may be describedherein using terminology commonly associated with 3G and/or 4G wirelesstechnologies, aspects of the present disclosure can be applied in othergeneration-based communication systems, such as 5G and later, includingNR technologies.

Example Wireless Communications System

FIG. 1 illustrates an example wireless network 100 in which aspects ofthe present disclosure may be performed. For example, the wirelessnetwork 100 may be a new radio (NR) or 5G network and may utilizesynchronization and broadcast channel designs presented herein. Forexample, the synchronization and broadcast channel designs may useflexible bandwidth allocations and may not be centered around the DCtone of the system bandwidth. UEs 120 may be configured to perform theoperations 1000 and other methods described herein and discussed in moredetail below. For example, UE 120 can detect a synchronization channeland a secondary synchronization signal (SSS) transmitted with thesynchronization channel. The UE 120 may demodulate a physical broadcastchannel (PBCH) using the SSS to obtain system information such as thedownlink bandwidth.

As illustrated in FIG. 1, the wireless network 100 may include a numberof base station (BSs) 110 and other network entities. A BS may be astation that communicates with UEs. Each BS 110 may providecommunication coverage for a particular geographic area. In 3GPP, theterm “cell” can refer to a coverage area of a Node B (NB) and/or a NodeB subsystem serving this coverage area, depending on the context inwhich the term is used. In NR systems, the term “cell”, BS, NextGeneration Node B (gNB), Node B, 5G NB, access point (AP), NR BS, NR BS,or transmission reception (TRP) may be interchangeable. In someexamples, a cell may not necessarily be stationary, and the geographicarea of the cell may move according to the location of a mobile BS. Insome examples, the BSs may be interconnected to one another and/or toone or more other BSs or network nodes (not shown) in the wirelessnetwork 100 through various types of backhaul interfaces such as adirect physical connection, a virtual network, or the like using anysuitable transport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a frequencychannel, a tone, a subband, a subcarrier, etc. Each frequency maysupport a single RAT in a given geographic area in order to avoidinterference between wireless networks of different RATs. In some cases,NR or 5G RAT networks may be deployed.

A BS may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a Closed Subscriber Group (CSG), UEs for users in the home,etc.). A BS for a macro cell may be referred to as a macro BS. A BS fora pico cell may be referred to as a pico BS. A BS for a femto cell maybe referred to as a femto BS or a home BS. In the example shown in FIG.1, the BSs 110 a, 110 b and 110 c may be macro BSs for the macro cells102 a, 102 b and 102 c, respectively. The BS 110 x may be a pico BS fora pico cell 102 x. The BSs 110 y and 110 z may be femto BS for the femtocells 102 y and 102 z, respectively. ABS may support one or multiple(e.g., three) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., a BS or a UE) and sends atransmission of the data and/or other information to a downstreamstation (e.g., a UE or a BS). A relay station may also be a UE thatrelays transmissions for other UEs. In the example shown in FIG. 1, arelay station 110 r may communicate with the BS 110 a and a UE 120 r inorder to facilitate communication between the BS 110 a and the UE 120 r.A relay station may also be referred to as a relay BS, a relay, etc.

The wireless network 100 may be a heterogeneous network that includesBSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc.These different types of BSs may have different transmit power levels,different coverage areas, and different impact on interference in thewireless network 100. For example, macro BS may have a high transmitpower level (e.g., 20 Watts) whereas pico BS, femto BS, and relays mayhave a lower transmit power level (e.g., 1 Watt).

The wireless network 100 may support synchronous or asynchronousoperation. For synchronous operation, the BSs may have similar frametiming, and transmissions from different BSs may be approximatelyaligned in time. For asynchronous operation, the BSs may have differentframe timing, and transmissions from different BSs may not be aligned intime. The techniques described herein may be used for both synchronousand asynchronous operation.

A network controller 130 may couple to a set of BSs and providecoordination and control for these BSs. The network controller 130 maycommunicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another, e.g., directly or indirectly via wirelessor wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless network 100, and each UE may be stationary or mobile. A UE mayalso be referred to as a mobile station, a terminal, an access terminal,a subscriber unit, a station, a Customer Premises Equipment (CPE), acellular phone, a smart phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet, a camera, a gaming device, a netbook, a smartbook, anultrabook, a medical device or medical equipment, a biometricsensor/device, a wearable device such as a smart watch, smart clothing,smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, asmart bracelet, etc.), an entertainment device (e.g., a music device, avideo device, a satellite radio, etc.), a vehicular component or sensor,a smart meter/sensor, industrial manufacturing equipment, a globalpositioning system device, or any other suitable device that isconfigured to communicate via a wireless or wired medium. Some UEs maybe considered evolved or machine-type communication (MTC) devices orevolved MTC (eMTC) devices. MTC and eMTC UEs include, for example,robots, drones, remote devices, sensors, meters, monitors, locationtags, etc., that may communicate with a BS, another device (e.g., remotedevice), or some other entity. A wireless node may provide, for example,connectivity for or to a network (e.g., a wide area network such asInternet or a cellular network) via a wired or wireless communicationlink. Some UEs may be considered Internet-of-Things (IoT) devices ornarrowband IoT (NB-IoT) devices.

In FIG. 1, a solid line with double arrows indicates desiredtransmissions between a UE and a serving BS, which is a BS designated toserve the UE on the downlink and/or uplink. A dashed line with doublearrows indicates interfering transmissions between a UE and a BS.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, etc. Each subcarriermay be modulated with data. In general, modulation symbols are sent inthe frequency domain with OFDM and in the time domain with SC-FDM. Thespacing between adjacent subcarriers may be fixed, and the total numberof subcarriers (K) may be dependent on the system bandwidth. Forexample, the spacing of the subcarriers may be 15 kHz and the minimumresource allocation (called a resource block (RB)) may be 12 subcarriers(or 180 kHz). Consequently, the nominal FFT size may be equal to 128,256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20megahertz (MHz), respectively. The system bandwidth may also bepartitioned into subbands. For example, a subband may cover 1.08 MHz(i.e., 6 RBs), and there may be 1, 2, 4, 8 or 16 subbands for systembandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR.

NR may utilize OFDM with a CP on the uplink and downlink and includesupport for half-duplex operation using TDD. A single component carrierbandwidth of 100 MHz may be supported. NR resource blocks may span 12sub-carriers with a sub-carrier bandwidth of 75 kHz over a 0.1 msduration. Each radio frame may consist of two half frames, each halfframe consisting of 5 subframes, with a length of 10 ms. Consequently,each subframe may have a length of 1 ms. Each subframe may indicate alink direction (i.e., DL or UL) for data transmission and the linkdirection for each subframe may be dynamically switched. Each subframemay include DL/UL data as well as DL/UL control data. UL and DLsubframes for NR may be as described in more detail below with respectto FIGS. 6 and 7. Beamforming may be supported and beam direction may bedynamically configured. MIMO transmissions with precoding may also besupported. MIMO configurations in the DL may support up to 8 transmitantennas with multi-layer DL transmissions up to 8 streams and up to 2streams per UE. Multi-layer transmissions with up to 2 streams per UEmay be supported. Aggregation of multiple cells may be supported with upto 8 serving cells. Alternatively, NR may support a different airinterface, other than an OFDM-based. NR networks may include entitiessuch CUs and/or DUs.

Beamforming generally refers to the use of multiple antennas to controlthe direction of a wavefront by appropriately weighting the magnitudeand phase of individual antenna signals (for transmit beamforming).Beamforming may result in enhanced coverage, as each antenna in thearray may make a contribution to the steered signal, an array gain (orbeamforming gain) is achieved. Receive beamforming makes it possible todetermine the direction that the wavefront will arrive (direction ofarrival, or DoA). It may also be possible to suppress selectedinterfering signals by applying a beam pattern null in the direction ofthe interfering signal. Adaptive beamforming refers to the technique ofcontinually applying beamforming to a moving receiver.

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed further below,the scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. BSs are not theonly entities that may function as a scheduling entity. That is, in someexamples, a UE may function as a scheduling entity, scheduling resourcesfor one or more subordinate entities (e.g., one or more other UEs). Inthis example, the UE is functioning as a scheduling entity, and otherUEs utilize resources scheduled by the UE for wireless communication. AUE may function as a scheduling entity in a peer-to-peer (P2P) network,and/or in a mesh network. In a mesh network example, UEs may communicatedirectly with one another in addition to communicating with thescheduling entity.

Thus, in a wireless communication network with a scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, and a mesh configuration, a scheduling entity and one ormore subordinate entities may communicate utilizing the scheduledresources.

FIG. 2 illustrates an example logical architecture of a distributedradio access network (RAN) 200, which may be implemented in the wirelesscommunication system illustrated in FIG. 1. A 5G access node 206 mayinclude an access node controller (ANC) 202. The ANC 202 may be acentral unit (CU) of the distributed RAN 200. The backhaul interface tothe next generation core network (NG-CN) 204 may terminate at the ANC202. The backhaul interface to neighboring next generation access nodes(NG-ANs) 210 may terminate at the ANC 202. The ANC 202 may include oneor more TRPs 208 (which may also be referred to as BSs, NR BSs, Node Bs,gNBs, 5G NBs, APs, or some other term). As described above, a TRP may beused interchangeably with “cell.”

The TRPs 208 may be a DU. The TRPs 208 may be connected to one ANC (ANC202) or more than one ANC (not illustrated). For example, for RANsharing, radio as a service (RaaS), and service specific ANDdeployments, the TRP may be connected to more than one ANC. A TRP mayinclude one or more antenna ports. The TRPs may be configured toindividually (e.g., dynamic selection) or jointly (e.g., jointtransmission) serve traffic to a UE.

The logical architecture may support fronthauling solutions acrossdifferent deployment types. For example, the logical architecture may bebased on transmit network capabilities (e.g., bandwidth, latency, and/orjitter). The logical architecture may share features and/or componentswith LTE. The NG-AN 210 may support dual connectivity with NR. The NG-AN210 may share a common fronthaul for LTE and NR.

The logical architecture may enable cooperation between and among TRPs208. For example, cooperation may be preset within a TRP and/or acrossTRPs via the ANC 202. An inter-TRP interface may not be used.

The logical architecture may support a dynamic configuration of splitlogical functions. As will be described in more detail with reference toFIG. 5, the Radio Resource Control (RRC) layer, Packet Data ConvergenceProtocol (PDCP) layer, Radio Link Control (RLC) layer, Medium AccessControl (MAC) layer, and a Physical (PHY) layers may be adaptably placedat the DU or CU (e.g., TRP or ANC, respectively). A BS may include acentral unit (CU) (e.g., ANC 202) and/or one or more distributed units(e.g., one or more TRPs 208).

FIG. 3 illustrates an example physical architecture of a distributed RAN300, according to aspects of the present disclosure. A centralized corenetwork unit (C-CU) 302 may host core network functions. The C-CU 302may be centrally deployed. C-CU functionality may be offloaded (e.g., toadvanced wireless services (AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions.The C-RU 304 may host core network functions locally. The C-RU 304 mayhave distributed deployment. The C-RU 304 may be close to the networkedge.

A DU 306 may host one or more TRPs (edge node (EN), an edge unit (EU), aradio head (RH), a smart radio head (SRH), or the like). The DU 306 maybe located at edges of the network with radio frequency (RF)functionality.

FIG. 4 illustrates example components of the BS 110 and UE 120illustrated in FIG. 1, which may be used to implement aspects of thepresent disclosure. For example, UE 120 and BS 110 may be configured toperform SSS based PBCH demodulation for flexible bandwidth allocation ofsynchronization and broadcast signals not centered around the DC tone,and procedures described herein (e.g., with reference to FIG. 10).

As described above, the BS 110 may be a gNB, TRP, etc. One or morecomponents of the BS 110 and UE 120 may be used to practice aspects ofthe present disclosure. For example, antennas 452, Tx/Rx 222, processors466, 458, 464, and/or controller/processor 480 of the UE 120 and/orantennas 434, processors 430, 420, 438, and/or controller/processor 440of the BS 110 may be used to perform the operations described herein andillustrated with reference to FIGS. 10-12.

FIG. 4 shows a block diagram of a design of a BS 110 and a UE 120, whichmay be one of the BSs and one of the UEs in FIG. 1. For a restrictedassociation scenario, the BS 110 may be the macro BS 110 c in FIG. 1,and the UE 120 may be the UE 120 y. The BS 110 may also be a BS of someother type. The BS 110 may be equipped with antennas 434 a through 434t, and the UE 120 may be equipped with antennas 452 a through 452 r.

At the BS 110, a transmit processor 420 may receive data from a datasource 412 and control information from a controller/processor 440. Thecontrol information may be for the Physical Broadcast Channel (PBCH),Physical Control Format Indicator Channel (PCFICH), Physical Hybrid ARQIndicator Channel (PHICH), Physical Downlink Control Channel (PDCCH),etc. The data may be for the Physical Downlink Shared Channel (PDSCH),etc. The processor 420 may process (e.g., encode and symbol map) thedata and control information to obtain data symbols and control symbols,respectively. The processor 420 may also generate reference symbols,e.g., for a primary synchronization signal (PSS), primarysynchronization signal (SSS), and cell-specific reference signal. Atransmit (TX) multiple-input multiple-output (MIMO) processor 430 mayperform spatial processing (e.g., precoding) on the data symbols, thecontrol symbols, and/or the reference symbols, if applicable, and mayprovide output symbol streams to the modulators (MODs) 432 a through 432t. Each modulator 432 may process a respective output symbol stream(e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator432 may further process (e.g., convert to analog, amplify, filter, andupconvert) the output sample stream to obtain a downlink signal.Downlink signals from modulators 432 a through 432 t may be transmittedvia the antennas 434 a through 434 t, respectively. As described in moredetail below, in some cases, synchronization, reference signals, andbroadcast signals may have a flexible bandwidth allocation and may notbe centered around the DC tone.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) 454 a through 454 r, respectively. Eachdemodulator 454 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 454 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 456 may obtainreceived symbols from all the demodulators 454 a through 454 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 458 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 120 to a data sink 460, and provide decoded control informationto a controller/processor 480.

On the uplink, at the UE 120, a transmit processor 464 may receive andprocess data (e.g., for the Physical Uplink Shared Channel (PUSCH)) froma data source 462 and control information (e.g., for the Physical UplinkControl Channel (PUCCH) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by thedemodulators 454 a through 454 r (e.g., for SC-FDM, etc.), andtransmitted to the BS 110. At the BS 110, the uplink signals from the UE120 may be received by the antennas 434, processed by the modulators432, detected by a MIMO detector 436 if applicable, and furtherprocessed by a receive processor 438 to obtain decoded data and controlinformation sent by the UE 120. The receive processor 438 may providethe decoded data to a data sink 439 and the decoded control informationto the controller/processor 440.

The controllers/processors 440 and 480 may direct the operation at theBS 110 and the UE 120, respectively. The processor 440 and/or otherprocessors and modules at the BS 110 may perform or direct, e.g., theexecution of the functional blocks illustrated in FIG. 10, and/or otherprocesses for the techniques described herein. processes for thetechniques described herein. The processor 480 and/or other processorsand modules at the UE 120 may also perform or direct, e.g., theexecution of the functional blocks illustrated in FIG. 10, and/or otherprocesses for the techniques described herein. The memories 442 and 482may store data and program codes for the BS 110 and the UE 120,respectively. A scheduler 444 may schedule UEs for data transmission onthe downlink and/or uplink.

FIG. 5 illustrates a diagram 500 showing examples for implementing acommunications protocol stack, according to aspects of the presentdisclosure. The illustrated communications protocol stacks may beimplemented by devices operating in a in a 5G system (e.g., a systemthat supports uplink-based mobility). Diagram 500 illustrates acommunications protocol stack including a Radio Resource Control (RRC)layer 510, a Packet Data Convergence Protocol (PDCP) layer 515, a RadioLink Control (RLC) layer 520, a Medium Access Control (MAC) layer 525,and a Physical (PHY) layer 530. In various examples the layers of aprotocol stack may be implemented as separate modules of software,portions of a processor or ASIC, portions of non-collocated devicesconnected by a communications link, or various combinations thereof.Collocated and non-collocated implementations may be used, for example,in a protocol stack for a network access device (e.g., ANs, CUs, and/orDUs) or a UE.

A first option 505-a shows a split implementation of a protocol stack,in which implementation of the protocol stack is split between acentralized network access device (e.g., an ANC 202 in FIG. 2) anddistributed network access device (e.g., TRP 208 in FIG. 2, which may bea DU). In the first option 505-a, an RRC layer 510 and a PDCP layer 515may be implemented by the central unit, and an RLC layer 520, a MAClayer 525, and a PHY layer 530 may be implemented by the DU. In variousexamples the CU and the DU may be collocated or non-collocated. Thefirst option 505-a may be useful in a macro cell, micro cell, or picocell deployment.

A second option 505-b shows a unified implementation of a protocolstack, in which the protocol stack is implemented in a single networkaccess device (e.g., access node (AN), new radio base station (NR BS), anew radio Node-B (NR NB), a network node (NN), or the like.). In thesecond option, the RRC layer 510, the PDCP layer 515, the RLC layer 520,the MAC layer 525, and the PHY layer 530 may each be implemented by theAN. The second option 505-b may be useful in a femto cell deployment.

Regardless of whether a network access device implements part or all ofa protocol stack, a UE may implement an entire protocol stack (e.g., theRRC layer 510, the PDCP layer 515, the RLC layer 520, the MAC layer 525,and the PHY layer 530).

FIG. 6 is a diagram showing an example format of a DL-centric subframe600 (e.g., also referred to as a downlink centric slot). The DL-centricsubframe 600 may include a control portion 602. The control portion 602may exist in the initial or beginning portion of the DL-centric subframe600. The control portion 602 may include various scheduling informationand/or control information corresponding to various portions of theDL-centric subframe 600. In some configurations, the control portion 602may be a physical DL control channel (PDCCH), as indicated in FIG. 6.The DL-centric subframe 600 may also include a DL data portion 604. TheDL data portion 604 may sometimes be referred to as the payload of theDL-centric subframe 600. The DL data portion 604 may include thecommunication resources utilized to communicate DL data from thescheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE).In some configurations, the DL data portion 604 may be a physical DLshared channel (PDSCH).

The DL-centric subframe 600 may also include a common UL portion 606.The common UL portion 606 may be referred to as an UL burst, a common ULburst, and/or various other suitable terms. The common UL portion 606may include feedback information corresponding to various other portionsof the DL-centric subframe 600. For example, the common UL portion 606may include feedback information corresponding to the control portion602. Non-limiting examples of feedback information may include an ACKsignal, a NACK signal, a HARQ indicator, and/or various other suitabletypes of information. The common UL portion 606 may include additionalor alternative information, such as information pertaining to randomaccess channel (RACH) procedures, scheduling requests (SRs), and variousother suitable types of information. As illustrated in FIG. 6, the endof the DL data portion 604 may be separated in time from the beginningof the common UL portion 606. This time separation may be referred to asa gap, a guard period, a guard interval, and/or various other suitableterms. This separation provides time for the switch-over from DLcommunication (e.g., reception operation by the subordinate entity(e.g., UE)) to UL communication (e.g., transmission by the subordinateentity (e.g., UE)). One of ordinary skill in the art will understandthat the foregoing is merely one example of a DL-centric subframe andalternative structures having similar features may exist withoutnecessarily deviating from the aspects described herein.

FIG. 7 is a diagram showing an example format of an UL-centric subframe700 (e.g., also referred to as an uplink centric slot). The UL-centricsubframe 700 may include a control portion 702. The control portion 702may exist in the initial or beginning portion of the UL-centric subframe700. The control portion 702 in FIG. 7 may be similar to the controlportion 602 described above with reference to FIG. 6. The UL-centricsubframe 700 may also include an UL data portion 704. The UL dataportion 704 may be referred to as the payload of the UL-centric subframe700. The UL portion may refer to the communication resources utilized tocommunicate UL data from the subordinate entity (e.g., UE) to thescheduling entity (e.g., UE or BS). In some configurations, the controlportion 702 may be a PDCCH.

As illustrated in FIG. 7, the end of the control portion 702 may beseparated in time from the beginning of the UL data portion 704. Thistime separation may be referred to as a gap, guard period, guardinterval, and/or various other suitable terms. This separation providestime for the switch-over from DL communication (e.g., receptionoperation by the scheduling entity) to UL communication (e.g.,transmission by the scheduling entity). The UL-centric subframe 700 mayalso include a common UL portion 706. The common UL portion 706 in FIG.7 may be similar to the common UL portion 606 described above withreference to FIG. 6. The common UL portion 706 may additional oralternative include information pertaining to channel quality indicator(CQI), sounding reference signals (SRSs), and various other suitabletypes of information. One of ordinary skill in the art will understandthat the foregoing is merely one example of an UL-centric subframe andalternative structures having similar features may exist withoutnecessarily deviating from the aspects described herein.

In one example, a frame may include both UL centric subframes and DLcentric subframes. In this example, the ratio of UL centric subframes toDL subframes in a frame may be dynamically adjusted based on the amountof UL data and the amount of DL data that are transmitted. For example,if there is more UL data, then the ratio of UL centric subframes to DLsubframes may be increased. Conversely, if there is more DL data, thenthe ratio of UL centric subframes to DL subframes may be decreased.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including aconfiguration associated with transmitting pilots using a dedicated setof resources (e.g., a radio resource control (RRC) dedicated state,etc.) or a configuration associated with transmitting pilots using acommon set of resources (e.g., an RRC common state, etc.). Whenoperating in the RRC dedicated state, the UE may select a dedicated setof resources for transmitting a pilot signal to a network. Whenoperating in the RRC common state, the UE may select a common set ofresources for transmitting a pilot signal to the network. In eithercase, a pilot signal transmitted by the UE may be received by one ormore network access devices, such as an AN, or a DU, or portionsthereof. Each receiving network access device may be configured toreceive and measure pilot signals transmitted on the common set ofresources, and also receive and measure pilot signals transmitted ondedicated sets of resources allocated to the UEs for which the networkaccess device is a member of a monitoring set of network access devicesfor the UE. One or more of the receiving network access devices, or a CUto which receiving network access device(s) transmit the measurements ofthe pilot signals, may use the measurements to identify serving cellsfor the UEs, or to initiate a change of serving cell for one or more ofthe UEs.

FIG. 8 illustrates an example of a wireless communication system 800supporting a number of zones, in accordance with aspects of the presentdisclosure. The wireless communication system 800 may include a numberof zones (including, e.g., a first zone 805-a (Zone 1), a second zone805-b (Zone 2), and a third zone 805-c (Zone 3)). A number of UEs maymove within or between the zones.

A zone may include multiple cells, and the cells within a zone may besynchronized (e.g., the cells may share the same timing). Wirelesscommunication system 800 may include examples of both non-overlappingzones (e.g., the first zone 805-a and the second zone 805-b) andoverlapping zones (e.g., the first zone 805-a and the third zone 805-c).In some examples, the first zone 805-a and the second zone 805-b mayeach include one or more macro cells, micro cells, or pico cells, andthe third zone 805-c may include one or more femto cells.

By way of example, the UE 850 is shown to be located in the first zone805-a. If the UE 850 is operating with a radio resource configurationassociated with transmitting pilot signals using a common set ofresources, such as an RRC common state, the UE 850 may transmit a pilotsignal using a common set of resources. Cells (e.g., ANs, DUs, etc.)within the first zone 805-a may monitor the common set of resources fora pilot signal from the UE 850. If the UE 850 is operating with a radioresource configuration associated with transmitting pilot signals usinga dedicated set of resource, such as an RRC dedicated state, the UE 850may transmit a pilot signal using a dedicated set of resources. Cells ofa monitoring set of cells established for the UE 850 within the firstzone 805-a (e.g., a first cell 810-a, a second cell 810-b, and a thirdcell 810-c) may monitor the dedicated set of resources for the pilotsignal of the UE 850.

Example Synchronization and Broadcast Channel Design with FlexibleBandwidth Allocations

As illustrated in FIG. 9, in certain radio access technology (RAT)networks, such as long term evolution (LTE), the synchronization channel904 (e.g., carrying primary synchronization signal (PSS), secondarysynchronization signal (SSS), and/or physical broadcast channel (PBCH))is centered around the DC tone 902 (also referred to as the DC carrier)of the system bandwidth. The DC tone is a null tone at the center of thesystem bandwidth. Thus, by detecting the null tone, the user equipment(UE) may be able to detect the center of the system bandwidth. Thus, ifthe UE knows signals are centered around the DC tone, the UE can detectthose signals based on the detection of the DC tone. The synchronizationchannel 904 may carry some system information.

In such systems, when the UE starts initial acquisition, the UE searcheswith a channel raster granularity (e.g., 100 KHz) to determine thepresence of synchronization signals (e.g., PSS and SSS). A referencesignal 906, such as the cell-specific reference signal (CRS) sequencemay be centered with respect to DC tone 902. This allows the UE todetermine the CRS sequence before it acquires downlink system bandwidthinformation in PBCH. The CRS can be used to demodulate the PBCH, whichis also centered around the DC tone. Once the UE receives the PBCHcarrying system information such as the downlink bandwidth, the UE canuse that information to perform a random access channel (RACH) procedurewith the cell. As shown in FIG. 9, the RS may be centered around the DCtone for various system bandwidths, such as 5 MHz (RS 906), 10 MHz (RS908), or 80 MHz (RS 910).

In some cases, however, the synchronization channel and reference signalmay not be centered around the DC tone. In NR applications, to minimizeUE initial search complexity, the UE may search with a channel rasterwith a much coarser granularity compared to the “normal” channel rastermay be used. For example, the UE may search for the synchronizationchannel with a 1 MHz raster while the channel raster is with 100 KHz.With unlicensed or shared spectrum, the system bandwidth could be widerthan the channel sensing granularity. For example, the system bandwidthcould be 80 MHz while the channel sensing is per 20 MHz. In order for UEto acquire the system when a node does not have full 80 MHz channelavailability, the synchronization channel could be transmitted on each20 MHz. In narrowband Internet-of-Things (NB-IOT) applications, afraction of the downlink bandwidth is typically used to transmit NB-IOTsignal. In these scenarios, the synchronization channel may not becentered with respect to the DC tone of system bandwidth.

Aspects of the present disclosure provide flexible synchronizationchannel and PBCH designs, for example, that may allow synchronizationchannels that are not centered around DC tone, but still allow the UE toefficiently detect the synchronization channel, read the PBCH, anddetermine system bandwidth.

FIG. 10 is a flow diagram illustrating example operations 1000 forwireless communications. Operations 1000 may be performed, for example,by a UE (e.g., UE 120), in accordance with aspects of the presentdisclosure. While not shown, certain aspects of the present disclosurealso provide a method for wireless communications by a base station thatmay be considered complementary to the UE operations 1000 above (e.g.,for generating the synchronization and PBCH channels detected and readby the UE).

The operations 1000 begin, at 1010, by detecting a synchronizationchannel and a secondary synchronization signal (SSS) transmitted withthe synchronization channel. At 1020, the UE demodulates a physicalbroadcast channel (PBCH) based on the SSS. At 1030, the UE determinessystem bandwidth corresponding to the downlink bandwidth based on systeminformation in the PBCH.

FIG. 11 illustrates one example of a synchronization channel design(e.g., referred to as synchronization signal (SS) block). As shown inFIG. 11, the synchronization channel (or block) 1100 includes one PSSsymbol, one SSS symbol, and 2 PBCH symbols in the subframe (e.g., 500 μssubframe). The illustrated SS block (or subframe) example also includesa one-symbol measurement reference signal (MRS) (e.g., shown as MRS-C).The illustrated SS block (or subframe) example also includes DL commonburst, DMRS, UL common burst, and guard period (G) portions (asdescribed above with reference to FIGS. 6 and 7). After receivingminimum system information in the PBCH, the UE may receive remainingsystem information (RMSI), for example, in a physical downlink sharedchannel (PDSCH). Since in NR, the signals (e.g., signals within a SSblock) may not be centered around the DC tone, techniques andsynchronization channel design are desirable that allow the UE to detectthe PBCH, before obtaining DL bandwidth information.

Example SSS or Dedicated RS Demodulated PBCH

According to certain aspects, one solution is to allow for PBCHdemodulation with a reference signal, such as SSS or some otherdedicated RS for PBCH. The SSS or other RS may not depend on thedownlink bandwidth or the location of the synchronization channel withinthe downlink bandwidth.

According to certain aspects, the location of the dedicated RS may befixed relative to that of the synchronization channel. In one example,the dedicated RS may be located within the synchronization channelbandwidth. Once the UE acquires downlink bandwidth information from thePBCH, an MRS sequence can be determined (e.g., and generated)accordingly.

Example MRS Demodulated PBCH

According to certain aspects, a PBCH may be demodulated with an MRS. Asillustrated in FIG. 12, the synchronization channel 1202 is not centeredaround the DC tone. The MRS may have a wider bandwidth (e.g., 5 MHz forMRS 1204, 10 MHz for MRS 1206, and 80 MHz for MRS 1208) than thesynchronization channel 1202 and PBCH.

The UE may also use the MRS to perform measurements after initialacquisition. In some cases, the MRS sequence may always be centered withrespect to the synchronization channel, but independent of the actualsynchronization channel location or system bandwidth, as shown in FIG.12.

In some cases, the MRS sequence may be based on the system bandwidth,however, portions of the MRS spanning into the synchronization regionmay be overwritten (e.g., punctured) with another sequence which doesnot depend on the synchronization channel location or system bandwidthas shown in FIG. 13.

Example Synchronization Channel Offset Indication

According to certain aspects, the synchronization channel offset may besignaled to the UE. For example, the frequency offset of thesynchronization channel with respect to the DC tone may be indicated. Asshown in FIG. 14, the indication of the synchronization channel offsetmay be signaled in the ESS (e.g., enhanced synchronization signal)channel. The UE may use the synchronization channel offset indication todetermine the location of the synchronization channel to obtain the RSsequence used for PBCH demodulation.

Alternatively, the synchronization channel offset can be signaled to theUE implicitly, via the selection of PSS/SSS hypothesis. In other words,different combinations of PSS/SSS may be selected to signal differentSYNC channel offsets. In this case, the UE may obtain thesynchronization channel offset via PSS/SSS detection and use the offsetto derive the RS sequence for use in PBCH demodulation.

Example Multiple Hypotheses PBCH Decoding

In some cases, the signaling techniques described above may provide onlypartial information regarding the PBCH location. To resolve (e.g.,determine) any information about PBCH location that remains incompleteafter the use of any of those techniques, the UE may attempt to decodemultiple PBCH hypotheses. As an example, to reduce complexity of ESS-Cor SSS detection, only partial information related to thesynchronization channel offset may be signaled to the UE and multiplePBCH locations may be possible candidates.

As another example, the relative offset between the synchronizationchannel and the PBCH or between the synchronization channel and the MRSmay not be completely specified. Considering the example case ofunlicensed spectrum with 4 groups of 20 MHz spectrum, thesynchronization channel may be repeated only in a subset of the groups.In such cases, the UE may attempt to decode the corresponding possiblePBCH candidates.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112, sixth paragraph, unless the element is expressly recitedusing the phrase “means for” or, in the case of a method claim, theelement is recited using the phrase “step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal (see FIG. 1), a user interface (e.g., keypad, display, mouse,joystick, etc.) may also be connected to the bus. The bus may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, power management circuits, and the like, which are wellknown in the art, and therefore, will not be described any further. Theprocessor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer-readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For example, instructions for perform the operations describedherein and illustrated in FIGS. 10-12.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method for wireless communications by a userequipment (UE), comprising: receiving a reference signal dedicated fordemodulating a physical broadcast channel (PBCH), the reference signalcomprising a sequence that is independent of at least one of: a downlinkbandwidth or a location of a synchronization signal (SS) block within asystem bandwidth; searching for the PBCH within the system bandwidth;and demodulating the PBCH based on the reference signal dedicated fordemodulating the PBCH.
 2. The method of claim 1, wherein searching forthe PBCH comprises searching according to a synchronization raster thatis not centered around a direct current (DC) tone of the systembandwidth.
 3. The method of claim 1, wherein searching for the PBCHcomprises searching according to a synchronization raster having acoarser granularity than a channel raster for other channels in thesystem bandwidth.
 4. The method of claim 1, wherein the SS block is notcentered around a direct current (DC) tone of a system bandwidth.
 5. Themethod of claim 1, wherein a frequency location of the reference signaldedicated for demodulating the PBCH is fixed with respect to a locationof the SS block.
 6. The method of claim 1, wherein the reference signaldedicated for demodulating the PBCH is within the SS block.
 7. Themethod of claim 1, wherein demodulating the PBCH comprises: determiningmultiple PBCH candidates; and evaluating the multiple PBCH candidates.8. The method of claim 1, wherein: the SS block comprises a secondarysynchronization signal (SSS) with at least one symbol, the PBCHcomprises two symbols in the SS block, and the SS block furthercomprises a one-symbol primary synchronization signal (PSS)time-division multiplexed (TDM) with the SSS and the PBCH.
 9. The methodof claim 1, further comprising, after demodulating the PBCH, receivingremaining system information (RMSI), not included in the PBCH, in aphysical downlink shared channel (PDSCH).
 10. An apparatus for wirelesscommunications, comprising: means for receiving a reference signaldedicated for demodulating a physical broadcast channel (PBCH), thereference signal comprising a sequence that is independent of at leastone of: a downlink bandwidth or a location of a synchronization signal(SS) block within a system bandwidth; means for searching for the PBCHwithin the system bandwidth; and means for demodulating the PBCH basedon the reference signal dedicated for demodulating the PBCH.
 11. Theapparatus of claim 10, wherein searching for the PBCH comprisessearching according to a synchronization raster that is not centeredaround a direct current (DC) tone of the system bandwidth.
 12. Theapparatus of claim 10, wherein searching for the PBCH comprisessearching according to a synchronization raster having a coarsergranularity than a channel raster for other channels in the systembandwidth.
 13. The apparatus of claim 10, wherein the SS block is notcentered around a direct current (DC) tone of a system bandwidth. 14.The apparatus of claim 10, wherein a frequency location of the referencesignal dedicated for demodulating the PBCH is fixed with respect to alocation of the SS block.
 15. The apparatus of claim 10, wherein thereference signal dedicated for demodulating the PBCH is within the SSblock.
 16. The apparatus of claim 10, wherein demodulating the PBCHcomprises: determining multiple PBCH candidates; and evaluating themultiple PBCH candidates.
 17. The apparatus of claim 10, wherein: the SSblock comprises a secondary synchronization signal (SSS) with at leastone symbol, the PBCH comprises two symbols in the SS block, and the SSblock further comprises a one-symbol primary synchronization signal(PSS) time-division multiplexed (TDM) with the SSS and the PBCH.
 18. Theapparatus of claim 10, further comprising, after demodulating the PBCH,receiving remaining system information (RMSI), not included in the PBCH,in a physical downlink shared channel (PDSCH).
 19. An apparatus forwireless communications, comprising: a memory; and at least oneprocessor coupled with the memory and configured to: receive a referencesignal dedicated for demodulating a physical broadcast channel (PBCH),the reference signal comprising a sequence that is independent of atleast one of: a downlink bandwidth or a location of a synchronizationsignal (SS) block within a system bandwidth; search for the PBCH withinthe system bandwidth; and demodulate the PBCH based on the referencesignal dedicated for demodulating the PBCH.
 20. The apparatus of claim19, wherein the at least one processor is configured to search for thePBCH by searching according to a synchronization raster that is notcentered around a direct current (DC) tone of the system bandwidth. 21.The apparatus of claim 19, wherein the at least one processor isconfigured to search for the PBCH by searching according to asynchronization raster having a coarser granularity than a channelraster for other channels in the system bandwidth.
 22. The apparatus ofclaim 19, wherein the SS block is not centered around a direct current(DC) tone of a system bandwidth.
 23. The apparatus of claim 19, whereina frequency location of the reference signal dedicated for demodulatingthe PBCH is fixed with respect to a location of the SS block.
 24. Theapparatus of claim 19, wherein a frequency location of the referencesignal dedicated for demodulating the PBCH is within the SS block. 25.The apparatus of claim 19, wherein the at least one processor isconfigured to demodulate the PBCH by: determining multiple PBCHcandidates; and evaluating the multiple PBCH candidates.
 26. Theapparatus of claim 19, wherein: the SS block comprises a secondarysynchronization signal (SSS) with at least one symbol, the PBCHcomprises two symbols in the SS block, and the SS block furthercomprises a primary synchronization signal (PSS) time-divisionmultiplexed (TDM) with the SSS and the PBCH.
 27. The apparatus of claim19, wherein the at least one processor is configured to, afterdemodulating the PBCH, receive remaining system information (RMSI), notincluded in the PBCH, in a physical downlink shared channel (PDSCH). 28.A non-transitory computer readable medium storing computer executablecode thereon for wireless communications, comprising: code for receivinga reference signal dedicated for demodulating a physical broadcastchannel (PBCH), the reference signal comprising a sequence that isindependent of at least one of: a downlink bandwidth or a location of asynchronization signal (SS) block within a system bandwidth; code forsearching for the PBCH within the system bandwidth; and code fordemodulating the PBCH based on the reference signal dedicated fordemodulating the PBCH.
 29. The non-transitory computer readable mediumof claim 28, wherein searching for the PBCH comprises searchingaccording to a synchronization raster that is not centered around adirect current (DC) tone of the system bandwidth.
 30. The non-transitorycomputer readable medium of claim 28, wherein searching for the PBCHcomprises searching according to a synchronization raster having acoarser granularity than a channel raster for other channels in thesystem bandwidth.